Dual Axis Vertical Reference System

Transcription

1 Dual Axis Vertical Reference System Owner s Manual PART NUMBER: VRS-S232-1AD WATSON INDUSTRIES, INC MELBY STREET EAU CLAIRE, WI Phone: (715) FAX: (715) support@watson-gyro.com 1

2 Table of Contents Introduction... 3 Product Description... 3 Installation... 3 Orientation:...3 Mounting:...3 Environment:...3 Power:...4 Theory of Operation... 4 Operation... 5 Special Operation Modes...5 Reference Mode...5 Free Mode...5 Specifications... 6 Analog Output... 7 RS-232 Digital Output... 7 RS-232 Output Format... 7 RS-232 Input Commands... 8 Connections... 9 Dimensions WARNING DISCLAIMER WARRANTY PRODUCT LIFE Customer Service Determining and Setting Output Channels...13 Setting Output Format...14 Appendix B Watson Industries prides itself on solving customer problems and serving their needs in a timely fashion. This manual is intended to facilitate this goal and to provide written information about your product. We ask that you carefully read this manual. Becoming familiar with the manual will help you understand the product s capabilities and limitations, as well as provide you with a basic understanding of its operation. If, after reading the manual, you require further assistance, do not hesitate to call Watson Industries with your questions and comments. CAUTION! Watson Sensors are rugged devices that have been used successfully in a number of harsh environments. The components have been qualified to withstand a mechanical shock of 1000g 's or greater, and most enclosures provide near that level of protection. However, dropping a sensor from waist height onto a hard floor can cause a shock level of 600g's. At this level, given some resonance, damage is possible. 2

3 Introduction The Watson Industries Vertical Reference represents a significant advancement in inertial sensor technology. It is a highly accurate and rugged device with many advantages over other types of angular rate and incline-sensing devices. This manual describes operation of the Watson Industries Vertical Reference and also provides useful application information to the system designer. Product Description The Watson Industries Vertical Reference System (VRS) is an entirely solid-state sensor that provides exceptional rejection from the adverse effects of inertia and short-term lateral accelerations. It does this through the use of both an accelerometer based vertical reference and an angular rate sensor which is integrated to provide additional information on angular position. It can be a functional replacement for mechanical gyros which are often more expensive and which cannot provide the reliability of a solid-state sensor. Theory of operation is described with more detail on page 4. The specifications, size and pinouts are described later in this document The Watson Vertical References provide for two types of analog output voltages. One is proportional to angular rate and the other is proportional to angular displacement. Full-scale analog outputs produce an output of ±10 volts dependent upon the direction of angular position or rotation. During rotation, positive voltage output occurs in the direction of the rotational arrow on the case. At horizontal and zero angular rotation rate, both outputs for displacement and rotation rate are near zero. A power supply, providing +10 to +30 Volts DC, is required to operate the unit. Special options in power supply, output voltage, scale calibration, and special packaging are available as custom units. Pricing and delivery information on custom units is available by contacting the factory. Installation Orientation: The base plate of the unit is to be mounted on top of a horizontal surface with the connector toward the forward direction of the vehicle. The VRS drawing, with wire call outs, is located in Figure 2. The VRS is a rugged device and will withstand harsh environments. However, due attention needs to be paid to the nature of the sensor and its prime function, which is to measure attitude and motion. Mounting: The unit has four 0.15 diameter mounting holes for using 6-32 screws. A mounting plate is provided for a flat surface mount. The unit may be adhesively mounted at any of its surfaces. If high shock loads are expected, greater than 10G or repeated shocks greater than 5G, the appropriate shock mounting should be used to prevent damage. Vibration environments of over 2.5 G rms would also require shock mounts or vibration isolation. Environment: Avoid mounting sites that are subject to significant temperature variation over the duration of the test. Temperature variation will induce significant rate sensor bias drift, which will reflect in poor attitude accuracy. 3

4 For shipboard applications, install the sensor near the center of gravity. For all applications, it is preferable to install the device where linear dynamic effects are minimized. Power: This unit has an internal regulator to allow operation over a wide voltage input range. Best operation is obtained at either +12 or +24 VDC level, although operation is fully satisfactory down to +10 VDC and up to +30 VDC. The power ground is isolated from the signal ground. Power consumption of the unit is 1.8W. The VRS power system is isolated from the VRS signal system. Internal capacitors are provided to remove a reasonable level of power line noise, however, capacitors should be added for long power line wiring or if noise is induced from other loads on the circuit. Theory of Operation In order to obtain an accurate signal in both the short-term and in the long-term, the Vertical Reference relies upon a Watson Industries angular rate sensor (ARS) combined with solid-state accelerometers. The position output is generated by integrating the angular rate output. This signal is compared with the output from the accelerometer and the resultant error signal is passed through a long time constant filter and fed back as a bias to the rate sensor. The system is damped by sending a portion of the error directly to the position integrator. By using a long time constant, the effect of the short-term errors in the accelerometer is minimized. Thus, the adverse effects of inertia, damping and short-term lateral accelerations on the pendulum essentially do not show up on the vertical reference output. See Figure 1 for system overview. The solid-state angular rate sensor used here works on the basic principle of detecting coriolis forces. These forces are generated when a moving particle is rotated. To use the coriolis effect to detect angular rotation, a solid structure is forced to vibrate normally at its resonant frequency. The vibration provides the structure with a linear velocity component. When the structure is rotated, the coriolis forces cause the vibration motion of the structure to be coupled to another vibration mode or plane of the structure. The magnitude of this secondary vibration is proportional to the angular rate of turn. 4

5 Operation In normal operation, the VRS takes data from its internal rate sensors and integrates them in a closed loop system, with the accelerometers as a long-term reference, to generate the Bank, and Elevation data. In most cases, these algorithms provide for very stable and accurate output signals; however, the user should be aware that exceeding the normal ranges of the sensors would affect accuracy. For example, while custom VRS units may have differing ranges, the rate gyros in a typical VRS have a maximum rate of 100 /s. Care should be taken not to exceed this rate because the closed loop system will receive inaccurate rate data. This will result in errors in the angle output signals. Special Operation Modes Reference Mode This mode is usually used for calibration or diagnostics. When in reference mode, the VRS will output data generated directly from the sensor reference signals rather than as a product of the closed loop integration used for normal operation. The reference command provides the same sensor information as in normal operation mode with the following differences: Bank and Elevation are obtained directly from the accelerometers - no gyro stabilization. Angular Rate Sensors are not close-loop bias corrected. The reference mode can be selected either through the terminal mode, or by an analog logic command. Note that reference mode is never a default setting. It must be re-selected when repowering the unit. Free Mode While in Free Mode, the VRS will output data from the sensors without correction by the references. For example, the Bank Angle data output in Free Mode is calculated directly from the X-axis Rate Sensor. In this case, the angle is a direct integration of the roll rate. Free Mode can be used to totally reject effects from dynamic accelerations, but accuracy degrades with time. It is intended for use over periods of a few minutes at a time. This mode provides similar sensor information as in normal operation mode with the following differences: Bank and Elevation are obtained directly from the rate gyros. Angular Rate Sensors are not close-loop bias corrected. Free mode can be accessed either through terminal mode, or by an analog logic command. Note that free mode is never a default setting. It must be re-selected when re-powering the unit. The user should not enter free mode until after the VRS is initialized and its readings are stable. 5

6 Specifications Attitude Range: Bank ±180 (±30 ) Digital (Analog) Range: Elevation ±90 (±30 ) Digital (Analog) Resolution: 0.02 Binary mode (14 bit) Analog Scale Factor: 3 /V ±10V Output Accuracy: Static ±0.5 (up to 75 ) * Accuracy: Dynamic ±2% Angular Rate Range: Roll, Pitch ±100 /sec Resolution: /sec Binary mode (14 bit) Analog Scale Factor: 10 /sec/v ±10V Output Scale Factor Accuracy: 2% Bias: Roll, Pitch < 0.3 /sec Non-Linearity < 0.05% Full scale range Bandwidth 20 Hz Acceleration Range: X, Y, Z ±10g Resolution: 4mg Scale Factor Accuracy: 1% Bias: X, Y, Z < 10mg Non-Linearity: 0.1% Full scale range Bandwidth: 20 Hz Environmental Temperature: Operating -40 C to +85 C Temperature: Storage -55 C to +85 C Vibration: Operating 2.5g rms 20 Hz to 2 khz Vibration: Survival 10g rms 20 Hz to 2 khz Shock: Survival 500g 10ms ½ sine wave Electrical Frame Rate Hz Maximum Startup Time: Data 5 sec Startup Time: Fully operational 10 sec Input Power: 10 to 30VDC 1.8W Input Current: 12VDC 24VDC Digital Output RS-232 Analog Output ±10VDC Analog Output Impedance: 300 Ohm Per line Physical Axis Alignment: < 0.25 Size: Including Mounting Flanges 3.24 W x 5.78 L x 2.38 H 8.2 x 14.7 x 6.0 (cm) Weight: 21oz (1.3lb) 590g (0.59kg) Connection: RS-232 / Analog Outputs 9 pin female D subminiature Connection: Power 9 pin male D subminiature * Actual accuracy can be calculated as the listed percentage multiplied by the change in value over the entire dynamic maneuver. Specifications are subject to change without notice 6

7 Analog Output Analog signals are output from a 12 bit digital to analog converter through an operational amplifier. Each analog output has a 300 ohm resistor in series to eliminate oscillations from high capacitance loads. The output range for all of the analog output channels is ±10 Volts with respect to the common signal ground. The analog outputs can be found on the 9-pin female D-Sub connector. The outputs include: Signal Pin Range Output Range 0 VDC Scale Factor Bank 6 ±30 ±10V 0 3 /V Elevation 7 ±30 ±10V 0 3 /V Roll Rate (X Axis) 8 ±100 /s ±10V 0 /s 10 /s/v Pitch Rate (Y Axis) 9 ±100 /s ±10V 0 /s 10 /s/v Note that the analog switches are disabled after certain serial commands are sent to the unit. This prevents software/hardware switch conflicts. RS-232 Digital Output The Digital RS-232 outputs can be found on the 9-pin female D-Sub. The Digital output pin map can be found on page 9. The RS-232 signals are referenced to the Signal Ground. The digital connections are: 1. RXD is the data receive line pin 3. The commands are sent to unit on this line. 2. TXD is the data transmit line pin 2. User Receives data on this line. 3. Signal Ground for RS-232 signals is on pin 5. RS-232 Output Format The nominal RS-232 output on the 9-pin female connector consists of a string of decimal ASCII characters sent asynchronously at regular intervals at about strings per second. The string is sent at 9600 baud with eight data bits, one stop bit and no parity. The contents of a typical string are formed as follows: (See Appendix A for information on how to change the data string.) 1. A single letter and a space used to indicate the start of the data string. The letter I indicates the start of an inertial data string. The letter R indicates the start of a Reference data string. If the letter is in lower case ( i or r ), an error over-range condition is indicated (see below). 2. A seven character string representing the bank angle starting with a space, then a + or a -, followed by three digits, a decimal point and one digit and for up to ±179.9 degrees. 3. A six character string representing the elevation angle starting with a space, then a + or a -, followed by two digits, a decimal point and one digit for up to ±89.9 degrees. 4. A six character string representing the X axis angular rate starting with a space, then a + or a -, followed by two digits, a decimal point and one digit for up to ±99.9 /second. 7

8 5. A five character string representing the Y axis angular rate starting with a space, then a + or a -, followed by two digits, a decimal point and one digit for up to ±99.9 /second. 6. The string is terminated by a carriage return. There will then be a short interval with no data transmission before the next string begins. Example: I <CR> bank angle (2) elev. angle (3) X axis Rate (4) Y axis rate (5) (6) space space space space (1) This may be reduced to attitude and heading information to improve the update rate to almost twice the previous rate by using special commands to modify the EEPROM of the unit. More channels are available for output see Appendix A. The system is protected from inadvertent write-over of the EEPROM by requiring two spacebar commands during the initialization interval to access the EEPROM or related functions. The baud rate may be changed from the nominal value of 9600 baud by modifying the default value in the EEPROM of the unit to 38400, 19200, or 4800 baud. A text header that is sent by the VRS during initializations identifies the unit by part number and by serial number and gives the date of last calibration. Additionally, a line of text characters that identifies the data channel columns is sent if the serial output is set to ASCII decimal. This whole message can be temporarily or permanently suppressed or restored by a * command from the interfacing computer. Data transmission sent by the VRS can also be suppressed or restored by a + command from the interfacing computer. The error over range condition is indicated by the use of a lower case i or r when the calculated attitude error exceeds the ranges listed above. Internal functions that require these error values are disabled while the condition exists. The system will continue to operate in an extended time constant mode with a low level of error accumulation until the condition is cleared. Occasional blips of this condition are expected with no detectable affect on the resulting data. The other output format available is a binary format. The binary format provides generally the same information as the decimal ASCII format, but in a compact binary file format. In this format, there are nominally 9 bytes sent that represent 4 fourteen-bit output channels followed by a carriage return. Again, this may be reduced to attitude information to improve the update rate (in this case the rate would be Hz) by using special commands to modify the EEPROM of the unit. This format is for highly experienced users only. Consult the factory for further details. RS-232 Input Commands The RS-232 input commands are provided for the purpose of unit test and installation set-up. The same parameters are used as for the output (9600 baud ASCII nominal, or as reset in the units EEPROM). There are eight commands intended for use by the user (others are used at the factory for alignment and calibration). 8

9 1. An R or r will set the outputs (analog and serial) to their Reference Command modes. This mode is used in installation to physically align the unit. Double spacebar at initialization is required for access to this command. 2. An I or i will clear the Reference Command mode if it had been set by the serial input. This is the default mode at power up and is the normal operating mode. Double spacebar at initialization is required for access to this command. 3. An F will disconnect the references from the attitude system and is the Coast Mode Command. This coast mode is used to make the system ignore the references during high maneuvers and brief disturbances. This mode is not intended for use except in brief intervals, since errors will grow geometrically. 4. A K will clear the Coast Mode Command. 5. An! will reinitialize the unit. Further, the access to initialization is inhibited such that a spacebar command must be sent within 5 seconds of the! command for initialization to be engaged. There are two output format serial commands: _ for decimal output and ^ for binary. See second part of Appendix A for more information on change output formats. There are several interface commands as well: : will toggle the output to send a frame of data upon receiving any non-command character and + will toggle the output for no output data. These and other changes are made non-volatile in the unit on EEPROM by keying in the quote ( ) character. Double spacebar at initialization is required for access to these commands. The & command calls a menu which allows any of several parameters to be set. These are system time constants, selection of data channels for serial output and baud rate. Double spacebar at initialization is required for access to this command. The commands #, $, (, ), {, },, <, > and? are used by the Watson factory to calibrate the unit and should be used only with the assistance of the factory. If an undesired function is called, a Q, and sometimes Escape or a Delete will interrupt the command and return to operation with the least disturbance to the system. All other unspecified characters such as carriage return, line feed and space are ignored by the system. If there are problems with the system hanging up during the binary output mode, check for crosstalk between the serial transmit and receive line in your installation. In addition, check to see that the communications program used is not sending an echo. This will not happen in the decimal or hexadecimal modes because command characters recognized by the system are not produced in those modes. Connections 9 Pin Male Power Connector Pin Description 1 Power Ground to + 30 VDC 3-9 No Connection 9

10 9 Pin Female RS-232/Analog Output Connector Pin Description 1 No Connection 2 RS-232 TXD 3 RS-232 RXD 4 No Connection 5 Signal Ground 6 Bank (X) Angle Analog Output 7 Elevation (Y) Angle Analog Output 8 X Angular Rate Analog Output 9 Y Angular Rate Analog Output The RS-232 serial and analog output connections are referenced to Signal Ground on pin 5. Dimensions Z X FORWARD Y Y REV. P/N S/N PWR. S.F. WATSON IND., INC. EAU CLAIRE, WI USA support@watson-gyro.com INTERNATIONALLY PATENTED AND PATENTS PENDING CAUTION DELICATE INSTRUMENT HANDLE WITH CARE 10

11 WARNING Rough handling or dropping of this unit is likely to cause damage. Over-voltage and/or miswiring of this unit will cause damage. This unit should be protected against prolonged exposure to high humidity and/or salt air environments. DISCLAIMER The information contained in this manual is believed to be accurate and reliable; however, it is the user s responsibility to test and to determine whether a Watson Industries product is suitable for a particular use. Suggestion of uses should not be taken as inducements to infringe upon any patents. WARRANTY Watson Industries, Inc. warrants, to the original purchaser, this product to be free from defective material or workmanship for a period of two full years from the date of purchase. Watson Industries liability under this warranty is limited to repairing or replacing, at Watson Industries sole discretion, the defective product when returned to the factory, shipping charges prepaid, within two full years from the date of purchase. The warranty described in this paragraph shall be in lieu of any other warranty, express or implied, including but not limited to any implied warranty of merchantability or fitness for a particular purpose. Excluded from any warranty given by Watson Industries are products that have been subject to abuse, misuse, damage or accident; that have been connected, installed or adjusted contrary to the instructions furnished by seller; or that have been repaired by persons not authorized by Watson Industries. Watson Industries reserves the right to discontinue models, to change specifications, price or design of this product at any time without notice and without incurring any obligation whatsoever. The purchaser agrees to assume all liabilities for any damages and/or bodily injury that may result from the use, or misuse, of this product by the purchaser, his employees or agents. The purchaser further agrees that seller shall not be liable in any way for consequential damages resulting from the use of this product. No agent or representative of Watson Industries is authorized to assume, and Watson Industries will not be bound by any other obligation or representation made in connection with the sale and/or purchase of this product. PRODUCT LIFE The maximum expected life of this product is 20 years from the date of purchase. Watson Industries, Inc. recommends the replacement of any product that has exceeded the product life expectation. 11

12 Customer Service All repairs, calibrations and upgrades are performed at the factory. Before returning any product, please contact Watson Industries to obtain a Returned Material Authorization number (RMA). Return Address & Contact Information Watson Industries, Inc Melby Street Eau Claire, WI ATTN: Service Department Telephone: (715) Fax: (715) support@watson-gyro.com Returning the Product Product shall be packaged making sure there is adequate packing around all sides. Please write the words, FRAGILE, DELICATE INSTRUMENT in several places on the outside of the shipping container. Correspondence shall include: Customer s Name and Address Contact Information Equipment Model Number Equipment Serial Number Description of Fault It is the customer s responsibility to pay all shipping charges from customer to Watson Industries, including import and transportation charges. 12

13 Appendix A The following outputs are available via the RS-232 serial link. Their full-scale ranges are listed for both decimal and binary format. Inertial Output Label Full Scale Decimal Full Scale Binary Time Since Reset TM Bank BK ±179.9º ±180º Elevation EL ±89.9º ±180º X Acceleration XA ±9.99 g ±10 g Y Acceleration YA ±9.99 g ±10 g Z Acceleration ZA ±9.99 g ±10 g X Angular Rate XR ±99.9 º/s ±200 º/s Y Angular Rate YR ±99.9 º/s ±200 º/s Bank Pendulum (simulated) XI ±179.9º ±180º Elevation Pendulum (simulated) YI ±89.9º ±180º Temperature TP -40º to 88ºC -40º to 88ºC (7 bit) Status Bits ST 1 byte 1 byte Flag Bits FL 1 byte 1 byte The Flag Bits contains the following information: a) Bits 0-2 show the current system time constant, using the following equations: TC=2 (Flag Value + 1) b) Bit 3 - If set, reference command selected. c) Bit 4 - If set, Steady Turn Mode Selected d) Bit 5 - If set, Coast mode is selected. e) Bit 6 - If set, the analog switches are disabled. Determining and Setting Output Channels To determine which channels are present. Hook the unit up to your computers serial port. Use hyperterminal program to interface with unit. Turn on unit. Wait for the startup message to appear on display. Hit the space bar twice within the first 5 seconds of turn on. Sometimes it takes a few tries to get the hang of this. Wait for the data string to start transmitting. Now the unit will take in the keyboard commands. To determine which channel present, first type '&' This will bring up the menu: TYPE IN THE NUMBER OF YOUR SELECTION (OR 'Q' TO QUIT): 1 = ADJUST TIME CONSTANTS 2 = SET OUTPUT CHANNELS 3 = LIST CURRENT OUTPUT CHANNEL SELECTION 4 = SET NEW BAUD RATE typing in '3' will show which channels are currently active. To change which channels are output type '&'(this will bring up the menu again) 13

14 Now type '2' to set up channels The following message will appear: TO SET FOR OUTPUT FOR ANY OF THE FOLLOWING DATA ITEMS, PRESS Y TO AVOID ANY OF THE FOLLOWING DATA ITEMS, PRESS N TO QUIT AND DISREGARD ANY OTHER DATA, PRESS Q *** DO YOU WANT TO PROCEED? (Y/N/Q) To proceed type 'Y' Now each channel will come up one at a time For example: DO YOU WANT OUTPUT TIME SINCE RESET? Type 'Y' to output channel, type 'N' to remove channel When you get to bottom of list, this message will appear: Y = GOBACK, N = INSTALL DATA & QUIT, Q = QUIT DO YOU WANT TO TRY TO SET DATA AGAIN? To accept channels type 'N', then hit space bar output data to resume. To make this channel selection the default the next time you power the unit on type in'"' (double quote) Setting Output Format There are two output formats. Decimal output - _ Command Binary output ^ Command To change the output format: Hook the unit up to your computers serial port. Use hyperterminal program to interface with unit. Turn on unit. Wait for the startup message to appear on display. Hit the space bar twice within the first 5 seconds of turn on. Sometimes it takes a few tries to get the hang of this. Wait for the data string to start transmitting. Now the unit will take in the keyboard commands. Press the key Command corresponding to the format you want to switch into. (for example type _ to change into Decimal Format.) To make this format selection the default the next time you power the unit on type in'"' (double quote.) 14

15 Appendix B MSB Data Word LSB As the data words are received, the LSB is shifted left to shift out the sign bit. The MSB is then connected to the LSB as a 16 bit word. This word is then shifted left to shift out the sign bit. What remains is a signed fractional word with a resolution of 13 bits plus a sign bit. DATA STREAM Carriage Return WORD 1 WORD 2 WORD 3 WORD 4... WORD N 0x0D All of the data words have a high sign bit, but the delimiter byte is an ASCII carriage return character that has a low sign bit. The nominal interface settings are: Byte 9600 Baud 8 Bit Data 1 Start Bit 1 Stop Bit No Parity 15